Significance Nerve Growth Factor is a neurotrophic factor which has potential as a therapeutic agent in the treatment of neurodegenerative diseases. One potential route of administration is direct delivery to brain parachymal. Objectives To determine whether NGF delivered to the CNS by direct intraparenchymal infusion will diffuse over sufficient distances to influence the rostral-to-caudal extent of the cholinergic basal forebrain. This study directly impacts the potential therapy of Alzheimer[unreadable]s disease in humans, the most common neurodegenerative disorder. Results To date, substantially greater distances of NGF diffusion through the adult primate brain have been observed that previously expected. Whereas previous reports suggest that NGF infusions into the rodent brain will difuse for a distance of only 1 mm, findings using our infusion technique in both rodents and primates reveal substantially greater distances of NGF diffusions. Future Directions The ability of intraparenchymal NGF infusions to rescue degenerating basal forebrain cholinergic neurons will be assessed. Successful findings in these studies could lead to the development of this technique for the treatment of Alzheimer[unreadable]s disease.